This invention relates to an assembly for supporting a shaft and, more particularly, to a non-contacting support assembly for supporting a relatively long, rotating shaft without the use of grease lubricated bearings and associated apparatus.
There are several applications in which a relative long shaft must be supported for relative high-speed rotational movement. For example, the tail rotor drive shaft of a helicopter, or an interconnecting drive shaft of a tilt rotor aircraft must be supported in a manner to prevent misalignment of the shaft yet permit rotation of the shaft at relatively high supercritical speeds. Most systems for supporting these types of shafts employ a plurality of grease lubricated bearings and hanger brackets which are expensive, heavy and cumbersome and require heavy maintenance. Also, to accommodate angular misalignment, expensive and heavy couplings are required. Further, subcritical shafts have to be relatively stiff so that they can rotate at speeds below their resonant frequencies to prevent instability.
Additional problems arise when the shaft rotates at supercritical speeds since a damping element and/or a motion limiter, such as a squeeze film damper or a friction damper, is usually required. However, these devices must be made to precision tolerances, and require accurate shaft alignment and regular inspections and maintenance, all of which are expensive.
Therefore, what is needed is a relative inexpensive and lightweight support assembly for supporting a rotating shaft according to which the shaft does not contact the support structure or dampers and therefore does not require grease lubricated bearings, hangers and the like, while eliminating squeeze film dampers and friction dampers. Also, a support assembly of the above type is needed which requires relatively little maintenance yet enables the shaft to rotate at supercritical speeds while maintaining shaft stability and maintaining the shaft alignment to the desired shape and position.